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Staff writer NAGANO — Does this country really need more dams?

That’s the focus of a debate that has boiled up in Nagano Prefecture, which questions the central government’s long-held policy of pumping massive amounts of public money into dam projects.

Nagao Gov. Yasuo Tanaka listens to explanations from a prefectural official near the planned site of a dam on the Asakawa River in November.

The popular Nagano Gov. Yasuo Tanaka touched off the commotion Feb. 20 when he declared the prefecture needs no more dams. Tanaka has been keen on the issue since his inauguration in October, inspecting sites of controversial dam projects in Nagano.

“Construction of a concrete dam, in which tens of billions of yen are invested, causes unbearable damage to the natural environment,” the writer-turned-governor said in a statement. “I hope that diverse debates over flood control will take place across the country.”

Tanaka’s hope was met. His no-dam declaration immediately drew strong protests from his prefectural assembly as well as local and central government bureaucrats, attracting nationwide media attention.

Conservation groups and an increasing number of citizens agree with the governor, claiming the construction of huge dams and their access roads have led to muddied rivers and vast forest areas being submerged.

According to the Japan Dam Foundation, the nation has 2,704 dams of 15 meters or higher. Dozens of dams can be found along almost all major rivers in any given prefecture.

And when the 413 more dams planned or under construction are completed, every prefecture will have an average of 66 dams.

Nagano is no exception. The mountainous prefecture has 60 dams with 14 more planned, 12 of which are already approved.

The central government has long promoted dam construction on the nation’s numerous short, rapid rivers for two reasons: flood control and water supply. But at least one of these reasons seems to be tenuous.

Most experts now agree that overall water-storage capacity planned in current dam projects is excessive.

The Land, Infrastructure and Transport Ministry admits that the government, in long-term planning for dams, has repeatedly overestimated future water demand by a long shot.

In 1978, annual demand for industrial and tap water was predicted to reach 46.53 billion cu. meters in 1985. Actual demand was slightly above 30 billion cu. meters.

In 1987, the government revised the projection to 43.03 billion cu. meters for 2000. Actual demand, however, is estimated to have remained at 30 billion cu. meters.

When it comes to the flood-control argument, opinions are often split.

According to the Infrastructure Ministry, a champion of dams and other public works projects — about 50 percent of Japan’s population lives in areas theoretically vulnerable to floods.

“Japanese people settled in (lowlands) where they could grow rice,” said Tadashi Miyamura, a professor at Kanto Gakuin University in Yokohama who defends the government’s dam construction policy.

“People live on alluvial plains, which were formed with earth and sand carried by floods. You should stand on the assumption that a flood will occur.”

Indeed, dam construction accelerated in the aftermath of major typhoons and floods in the 1940s and 1950s that killed thousands of people.

Devastating floods are now rare, apparently due to the massive construction of dams and riparian works.

“Dam construction has passed its peak, and new projects should be strictly selected,” said Yutaka Takahashi, professor emeritus at Tokyo University and a longtime adviser to the former Construction Ministry, which is now part of the Land, Infrastructure and Transport Ministry.

Takahashi said, however, that some new dams are necessary for flood control and he does not deny the effectiveness of conventional dams.

But Teruyuki Shimazu, an antidam activist and researcher at the Tokyo Metropolitan Government’s Research Institute for Environmental Protection, disagrees.

“You can manipulate numerical formulas to work out a greater probability of flooding by using arbitrary parameters,” he said.

The decision to build a dam is based on complex, technical simulations that calculate the probability of extremely heavy rain over a long period, such as 100 years or 200 years.

Thus, to explain to the public the reason for such a decision, the government needs their confidence and needs to ensure thorough information disclosure.

As Shimazu pointed out, it is only in recent years that the government began releasing details of these rainfall simulations.

Kotaro Takemura, chief of the Land Ministry’s River Bureau, acknowledged the need for greater information disclosure and said ordinary residents — not just antidam activists — are eager to understand the technical details of dam projects.

But Takemura said it is difficult to gain the support of the people, whose values are increasingly diverse in recent years. He cited the protection of the “ayu” sweet fish, one of the causes of the antidam movement, as an example. The fish can only be seen in very clear water in mountain rivers.

“Some people may attach more value to protecting the ayu in a river” than reducing the risk of flooding, he said.

“From now on, the tasks of administrative officials will become more difficult because everyone will have a different sense of values,” he said.

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